1. Field of the Invention
The invention relates to a cooling system, and more particularly, to a cooling system that cools a heat generation source through the use of a vapor compression refrigeration cycle.
2. Description of Related Art
Hybrid vehicles, fuel cell-powered vehicles, electric vehicles and the like, which run by the driving force of a motor, have been drawing attention as a measure against environmental issues. In such a vehicle, electric apparatuses such as a motor, a generator, an inverter, a converter, a battery and the like generate heat by giving/receiving electric power. Therefore, these electric apparatuses need to be cooled.
In Japanese Patent Application Publication No. 2000-73763 (JP-2000-73763 A), there is described a cooling system for a hybrid vehicle. This cooling system includes a first cooling circuit that selectively or simultaneously cools an engine cylinder head and a drive motor, a second cooling circuit that cools the engine cylinder block, and a third cooling circuit that cools a strong electric control unit that performs drive control of the drive motor.
In the cooling system described in Japanese Patent Application Publication No. 2000-73763 (JP-2000-73763 A), a system that causes cooling water to circulate between a heat generator and a radiator is employed to cool electric parts, as in the case of a normal vehicle in which only an engine thereof is cooled. Such a system needs to be newly provided with a radiator for cooling the electric parts, and hence may decrease in vehicle mountability.
Thus, there has been proposed an art of cooling a heat generator with the aid of a vapor compression refrigeration cycle that is employed as a vehicular air conditioner. For example, in Japanese Patent Application Publication No. 2007-69733 (JP-2007-69733 A), there is described a system in which a heat exchanger that exchanges heat with air-conditioning air and a heat exchanger that exchanges heat with a heat generator are arranged in parallel with each other in a refrigerant passage that extends from an expansion valve to a compressor. This system cools the heat generator through the use of a refrigerant for an air conditioner. Further, in Japanese Patent Application Publication No. 2005-90862 (JP-2005-90862 A), there is described a cooling system in which heat generator cooling means for cooling a heat generator is provided in a bypass passage that bypasses a pressure reducer, an evaporator, and a compressor in an air-conditioning refrigeration cycle.
On the other hand, as regards a vehicular air conditioner, in Japanese Patent Application Publication No. 2003-285633 (JP-2003-285633 A), there is described a device that causes a refrigerant to pass through a storage heat exchanger having a cooling storage material during the operation of a compressor, and cools the refrigerant by stored cold energy of the cooling storage material to operate an air conditioner after the stoppage of the compressor. In Japanese Patent Application Publication No. 2011-1048 (JP-2011-1048 A), there is described a vehicular air-conditioning system in which a heat storage material of an in-vehicle heat storage unit stores a certain amount of heat and the in-vehicle heat storage unit exchanges the amount of heat with a heat exchange medium through a heat exchange process.
In the cooling system described in each of Japanese Patent Application Publication No. 2007-69733 (JP-2007-69733 A) and Japanese Patent Application Publication No. 2005-90862 (JP-2005-90862 A), a cooling route for cooling the heat generation source such as an electric apparatus or the like is incorporated in a vapor compression refrigeration cycle, and a refrigerant in a two-phase state, namely, a gas-liquid state is introduced into a refrigerant route that cools the heat generation source, after having passed through a pressure reducer. When the flow rate of the liquid-phase refrigerant for cooling the heat generation source decreases, the performance of cooling the heat generation source may deteriorate.